A conventional technique for obtaining tissue samples from within the body is aspiration biopsy. This technique is safe and minimally traumatic, utilizing a small, hollow needle which is inserted directly into the body to a desired point, whereupon a tissue sample is withdrawn, such as by vacuum aspiration. The needle is then withdrawn, but because of its relatively insignificant diameter, wound closure occurs substantially normally by muscular and tissue tension, generally without the need for sutures, cauterization, or the like.
For optimal effectiveness, of course, this technique requires that the tip of the needle be precisely accurately placed at the location of the tissues to be sampled, and it is a primary object of the principles of the present invention to provide means and methods for facilitating such placement.
Because of their superior imaging capability with minimal hazard or risk to the patient, ultrasound imaging techniques have achieved prominent use for the location of the needle during biopsy techniques. In one class of prior art system, exemplified by U.S. Pat. Nos. 3,721,227 to Larson et al., 4,108,165 to Kopp et al., 4,029,084 to Soldner, and German Pat. No. 24 55 401 to Videnskaber, a biopsy needle is inserted in the center of an ultrasound transducer or transducer array, parallel to the direction of propogation of the ultrasound energy, so that the biopsy needle shows on the ultrasound image only if it diverts from such parallel orientation.
In another class of prior art system, exemplified by U.S. Pat. No. 4,058,114 to Soldner, the biopsy needle is carried by angular aiming apparatus which in turn is mechanically coupled to a pointer overlying the ultrasound image field. As the needle angle is established, the pointer overlays the image and follows the progress of the needle.
In yet another class of prior art system, exemplified by U.S. Pat. Nos. 3,556,079 to Omizo and 4,249,539 to Vilkomerson et al., a transducer element at the skin and another one within or at the tip of the needle correspond with one another precisely to locate the needle in the image field.
These prior art systems have varying degrees of propriety and efficiency, depending upon the ultrasound system being utilized and the needs or requirements of the operating surgeon. Perhaps the least efficient are those which require parallel orientation of the propogating ultrasound energy and the needle, because of their failure to yield either clear composite images or accurate needle depth representation. Probably the most effective prior art systems are those exemplified by the Vilkomerson et al. patent, but they require special electronics and compact and expensive transducer elements mountable at the needle tip and removable through the biopsy needle.
It is an object of the present invention to provide ultrasonically guided biopsy needle systems and techniques which yield highly visible and well calibrated images including the needle during insertion, but which do not require separate active transducer elements associated with the needle.
Recently, a class of real time ultrasound imaging systems have become popular based on the sector scan rationale. For example, one such system is commercially available from Technicare Corporation under the tradename "AUTOSECTOR", and is exemplified in U.S. application Ser. No. 178,488 of Sorwick filed Aug. 15, 1980 now U.S. Pat. No. 4,330,874. Generally, sector scan systems employ rotating or oscillating transceiver mechanisms for sonic illumination of, and hence imaging of a sector of tissue which broadens with increasing distance from the transceiver. In the Sorwick style system, a stationary transducer and an oppositely facing, rotating inclined sonic mirror are located in a first, outboard portion of a scanner, the motor drive and control systems are located in a second, inboard portion of the scanner, and the outboard and inboard scanner are coupled in offset relationship by an intermediate section which transfers oscillatory motive force from the motor to the mirror/transducer section. The whole unit is conveniently hand held, but only the smaller, spatially offset outboard portion makes contact with the patient.
It is an object of the present invention to provide biopsy needle guide apparatus and techniques adapted for use in conjunction with sector scan systems, and more particularly those of the sort exemplified by the captioned Sorwick application.
Associated, but by no means less significant objects of the present invention, include provision of a design which avoids the need to sterilize the ultrasound scanner to be used in biopsy procedures, provision of guide systems which are not only precise, but are sufficiently inexpensive to permit disposability, and provision of guide mechanisms which protect valuable transducer head mechanisms, and avoid damage or misalignment due to forces to which the scan head is subjected during the biopsy procedure.